1. Field of the Invention
The present invention relates to a process and an apparatus for transporting printing products, in particular multi-sheet and folded printing products.
2. Description of the Related Art
An apparatus for transporting folded printed sheets arriving in an imbricated formation is disclosed in German Offenlegungsschrift 3,335,140 and the corresponding U.S. Pat. No. 4,566,582. This apparatus is provided with a belt conveyor leading past a branch-off point, and a removal conveyor, with a conveying-away direction parallel to the conveying direction, following the branch-off point downstream, viewed in the conveying direction of the belt conveyor, and arranged next to and in the same plane as the belt conveyor. A branching-off device is provided at the branch-off point in order to supply to the removal conveyor a part of the imbricated formation fed by the belt conveyor. The other part of the imbricated formation is guided unchanged past the branch-off point by means of the belt conveyor. In the fed imbricated formation, each printed sheet lies on the preceding one, viewed in the conveying direction, the leading edges of the printed sheets run at right angles to the conveying direction and the side edges are aligned with one another. The branching-off device has two rolls, arranged at the free end of an arm which can swivel about a vertical axis, driven in rotation and defining a conveying nip active in the diagonal direction of the fed printed sheets, the components, running parallel to the conveying direction of the belt conveyor, of the circumferential speed of these rolls being at least equal to the conveying speed of the belt conveyor. A shaft is, furthermore, swivelably mounted on the arm and carries at its free end a flap which precedes the lower roll upstream, viewed in the conveying direction. In order to branch off printed sheets from the fed imbricated formation, the arm is swiveled and lowered relative to the belt conveyor such that the tongue slips between two printed sheets of the imbricated formation lying on top of one another and feeds the printed sheet which comes to lie on the tongue, and the printed sheets following this printed sheet, viewed in conveying direction, to the conveying nip defined by the rolls. In order to retain the position of the printed sheets with respect to the conveying direction of the belt conveyor, the rolls act upon the printed sheets in a straight line which passes through the center of gravity of the printed sheets. In order to enable the printed sheets to be taken up by the rolls of the branching-off device, the fed imbricated formation is arranged on the belt conveyor offset laterally toward the branching-off device such that a relatively broad lateral edge region of the imbricated formation projects from the belt conveyor. The printed sheets taken up by the branching-off device are pushed on top of one another onto the removal conveyor in order to form a new imbricated formation which corresponds exactly to the fed imbricated formation. As soon as a sufficient number of printed sheets has been detached from the fed imbricated formation, the arm of the belt conveyor is swiveled away out of the edge region of the fed imbricated formation, carrying with it the last printed sheet fed to the conveying nip. Various measures must be taken in this known apparatus in order to allow the printed sheets which are to be supplied to the removal conveyor to be taken up. The imbricated formation must thus be arranged laterally offset on the belt conveyor. Moreover, the branching-off device has a complex design and must be designed such that it is able to be raised and lowered, be swiveled about the vertical axis and be displaced in a direction at right angles to the conveying direction.